Specific Drugs

The classification of drugs into their physiological or psychological actions (e.g., stimulants and sedatives), is unsatisfactory because a single drug may have several actions; it is preferable to classify drugs according to their pharmacodynamic actions (Table 3) (15).

3.1. Opiate Intoxication and Withdrawal

The characteristics of the medical syndromes in opiate intoxication, overdose, and withdrawal are given in Table 4. Opiates, such as heroin, may be taken orally, more usually injected, or smoked—chasing the dragon. The start

of withdrawal will vary in time with the different opioid drugs, and it should be remembered that the severity of withdrawal symptoms is influenced greatly by psychological factors (16); the environment of a police cell is likely to exacerbate these symptoms.

Chronic administration of opiate drugs results in tolerance (Table 5) to effects such as euphoria mediated by the opiate receptors and to the effects on the autonomic nervous system mediated by the noradrenergic pathways. Tolerance to heroin can develop within 2 weeks of commencing daily heroin use, occurs more slowly with methadone, and may go as quickly as it develops. With abrupt withdrawal of opiates, there is a "noradrenergic storm," which is responsible for many of the opiate withdrawal symptoms (Table 6). Cyclizine may be taken intravenously in large doses with opiates, because it is reported to enhance or prolong opioid effects, also resulting in intense stimulation, hallucinations, and seizures; tolerance and dependence on cyclizine may also result (17). Many opiate users are also dependent on benzodiazepines, and concurrent benzodiazepine withdrawal may increase the severity of opiate withdrawal (18).

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